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High Altitude

Discussion in 'CV Performance' started by johnr733, Jun 7, 2011.

  1. johnr733

    johnr733 New Member

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    I received the Performance kit marked 88 on it, (bike is an EVO bored to 88", ported heads, 530 cam). The supplied jets in the kit are 190 & 195. The bike is currently running a CV with a thunderslide which had a 185 main I lowered to 175 so I'd have some top end pick up. I live in Denver by the way.

    So before I install this i'm wondering if I need different size main jets. Your thoughts? or does your needle normally need larger mains.

    Thanks
  2. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi John, the kit supplied is indeed for a 88" engine however the kit will not work with a Thunderslide. Dynojet has their own proprietary jets, needle, and emulsion tube that will not work with other parts. CVP parts including the needle and emulsion tube are designed to work with any original Keihin, Harley and OEM. One reason you may have a smaller main jet than what is specified in the kit is DJ jets use their own sizing and is not standardized to OEM specs. Therefore a 175 main jet from Dynojet is not equal to the original 175 from Keihin. CVP jets are designed to the same specs as originally developed by Keihin to guarantee compatibility.

    What all this means to you... if you wish to stay with your installed Thunderslide unfortunately you can only use Dynojet brand parts (jets, needle, etc). To use the CVP kit you will need to change the slide back to a stock slide. If you opt to stay with your Thunderslide setup please contact me and we can discuss a return and refund.
  3. HarleysLR

    HarleysLR Active Member

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    john,
    Go with the CVP kit you're far better off with it,
    Jetting for an Evo at 5,000 ft should be around a 48 slow and a 185 + for main. I live in Colorado Springs and run a 48 - 190 in my CV carb. Our elevations is 6,000 ft plus, I go to Denver all the time and bike runs great there to. I'll be at Freedom Harley Saturday from 9:30 to 3:00 if you want to stop by and shoot the breeze. I'll be shinning boots for anyone who wants a free shine.
  4. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Hey DW, when are able to get the Meet and Greet together, would you suggest that I change the jetting on my Sportster as well?
  5. HarleysLR

    HarleysLR Active Member

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    No, It'll run fine up here, some how the cv adjust to changes in altitude pretty well on it's own, it wouldn't be worth it for the short time you'll be here. I don't change when I go to sea level and the bike runs good down there. What jets are you running?
  6. JohnnyBiker

    JohnnyBiker Well-Known Member

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    46 and 185
  7. chucktx

    chucktx Moderator Staff Member

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    your good to go johnny.........
  8. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Thanks Chucktx...:D
  9. FLHTbiker

    FLHTbiker Moderator Staff Member

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    Yea but you know it will probably change before next year. :D:roflmao:
  10. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Why??
  11. cowboy

    cowboy Moderator Staff Member

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    Cause they think you'll change them , your bike will run good up in colo we went from sea level to the mountains of nm & not even a miss from a carb bike & a efi bike
  12. kenfuzed

    kenfuzed Administrator Staff Member

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    Right, the CV carburetor is the only carb that can self regulate for changes in altitude. In fact several years back I built quit a few of these for a group building ultralite airplanes... but you won't find me test driving those!
  13. johnr733

    johnr733 New Member

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    I'm sorry, I wasn't as clear as I could have been. I have another stock CV carb I plan to take the slide out of and put in the carb which now has the thunderslide in it, (because the current thunderslided carb already has a brass fuel inlet and a ez adjust idle screw). So the slide won't be an issue. It was just the confusion on the jets. A 48 slow jet is much higher than the currently installed jet also. Currently running a 44.

    The reason I started looking into carb kits again is, I accelerate well up to about 55 then I slowly lose my ability to take off if i need to, unless I drop down to third gear or so. With the cam in this engine i should not be experiencing this. This improved when i changed from a 185 to a 175 main. So I hope you understand why I'm concerned about the jet sizes in the kit. Thanks again for
  14. kenfuzed

    kenfuzed Administrator Staff Member

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    I completely understand your concern. If your current jetting is installed along with the Thunderslide, that would explain why you are needing the smaller jets. The Thunderslide completely changes the jetting and needs of the engine. I believe that once the stock slide is installed you would find the jetting closer to what is being supplied in the kit.

    Jetting is based on displacement and overall volume of the engine. Though your engine started life as an Evo 1340, the fact that it has been bored to 88" (1450cc) and heads ported allows the engine to breath and flow at a similar rate to a Twin Cam 88. Once paired with the stock slide the kit's needle, spring, and jetting recommendation should put you in the ballpark for a well tuned machine. If concerned about over jetting you could start with the lowest recommendation for an 88" using this kit (46/190). In some rare instances an exhaust system can be so well tuned that flow and scavenging allows for a smaller main jet but its more the exception than the rule. If by chance you do need a lower jet size to make this work I would certainly set you up with what you need to make this all work, but for starters I recommend using the recommendations and a baseline.
  15. johnr733

    johnr733 New Member

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    Well got around to installing the kit, just my luck however, the diaphragm in the other CV carb, (the one with the stock slide) is ripped. Time to call Zanotti's I guess. I'll find out how good this kit is one of these days!
  16. chucktx

    chucktx Moderator Staff Member

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    i hate it when that happens!!! lol
  17. johnr733

    johnr733 New Member

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    Ok, got the kit installed with 46/190. Right now however, feels a little sluggish of idle. Midrange is nice though.
  18. HarleysLR

    HarleysLR Active Member

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    try adjusting the idle mixture screw
  19. johnr733

    johnr733 New Member

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    Man, getting this mixture screw just right seems to be a bit of a pain. Anyone know an easy technique?

    One of the other things i notice is the choke on the carb doesn't seem to work quite as well with the new jets. Any thoughts?

    Last question, I read that some people put a washer under their jet needle. What were they experiencing that prompted them to do that?

    Thanks for your help!
  20. JohnnyBiker

    JohnnyBiker Well-Known Member

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    Shimming it raises the needle.

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